Air conditioning system



Oct. 20, 1942.

W. L. MGGRATH AIR `CONDITIONING SYSTEM Filed June 25, 1938 3 Sheets-She-et* l :inventor William L Ml @with Gttorneg Oct. 20, 1942. w. x.. MQGRATH AIR CONDITIONING SYSTEM 3 Sheets-Sheet 2 Filed June 25, 1958 T0 HIGH PRESSURE SIUE OF COMPRESSOR T0 DISCHARGE SIDE 0F CONDENSER R E S N E N 0 C 0 T Snnentor Wllllmm 1L Mc (Gru Mh;

ahorn-eg Ot. 20, 1942. w, McGRATH 2,299,335

AIR coNDITIoNING sYs'rEu Filed June 25. 19:58 s sheets-sheet s William LMC Grubb Img@ //wf #M attorney y Patented Oct. 20, 1942 2,299,335 Am CONDITIONING SYSTEM William L. McGrath, St. Paul,

Minneapolis-Honeywell Minneapolis, Minn., a corporation of Delaware Application June 25, 1938, Serial No. 215,796

9 Claims.

'This invention relates to an air conditioning systemand more particularly to a system. for controlling the temperatureof a iluid used for cooling purposes.

In many air conditioning systems, well water is used for colling the temperature of air being circulated through a spacev to be conditioned and it is common practice to turn on the supply of Well water when cooling is required and when the temperature of the space has fallen to the predetermined value, the supply of well water is shut off. If the air being circulated over the coil through which the well water flows is not much warmer than the temperature t o which it is desired to lower the space, the well water leaving the coil will not`have been warmed up to a very high value and if this well water after flowing through the cooling coil is thrown away as is common practice,A much of the cooling value of this water will have been wasted.

In accordance with my invention I propose to control the flow of water through the coil in such a way that there will be a suillcient temperature rise of the water leaving the coil to insure that the water is being used to obtain the greatest cooling eil'ect thereof. I accordingly make use of a differential temperature controller whichv is responsive'h4 to the temperature of the water entering the coil and thewater leaving the coil to position the valve which controls the flow .of water through the coil in suc a way so as to insure a predetermined temperature rise of the water owing through the coil. rIhe amount of differential which is maintained between the inlet and exit of the coil may be varied in accordance with the cooling requirements of the space. In other words, it the temperature of the space is at a very high value then the differential in temperature between the inlet and.

exit of the' coil may be somewhat less than if the temperature in the space is at a lower value, in order that thev temperature within the space may bereduced in a shorter time than would be possible if a high temperature differential between the inlet and the outlet-of the coil were maintained at all times. In this way I am able to eiciently utilize the well water for cooling purposes .while at the same time effectively con' trolling the temperature wit-hin the space being cooled.

This same system may be utilized in other systems such as in refrigeration systems wherein -well water is utilized to cool the condenser of the refrigeration system.

It is therefore an object of my Minn., assignor to Regulator Company,

suitably control the ow of cooling fluid through a cooling coil so as to utilize the cooling capacity of the fluid at high eiciency.

More particularly itis an object of my invention to control the ow of well water through a cooling coil so as to maintain a predetermined temperature diiferential between the inlet and outlet of the coil for any particular temperature within the space being conditioned.

A further object of my invention is to provide means for controlling the flow of cooling water through a condenser of a refrigeration system by maintaining a predetermined temperature differential between the inlet and outlet of the condenser cooling water, which diierential may be compensated by the pressure on the high pressure side of the refrigeration system.

A further object of .my invention -is the provision of a novel temperature differential controller for controlling the ow of a cooling uid through a coil so as to maintain a predetermined temperature differential between the inlet and outlet of the coil.

Further objects and advantages will become apparent upon reference to the accompanying specication, claims. and appended drawings wherein like reference characters represent like parts in the various views, and in which:

Figure 1 is a diagrammatic view of one form of system embodying my invention;

Figure 2- is a modication of the system lshown in Figure 1 wherein the Water flowing to the cooling coil has a uniform inlet temperature;

Figure 3 is a modiiication of a portion of Figure 2 showing a slightly different control arrangement;

vFigure 4 is a view of my invention as applied to the condenser of a refrigeration system;

Figure 5is a modication of the system shown in Figure 4 utilizing a self contained differential controller for the inlet valve;

Figure 6 is a viewin cross section of a self contained dierential controller forv operating the valve which controls the flow of water to the cooling coil.

Referring now to Figure 1, an air conditioning chamber is represented generally by the relerence character I0, this chamber including a fresh air inlet -I I, a return air inlet I2, and an outlet I3 communicating with a space I5 to be conditioned. A fan I6 driven by a motor II is provided for drawing air through the chamber I0 and exhausting it into the space I5. Mounted within the chamber I0 is a cooling coil invention to I8' over which the air being circulated through .pinion 23 carried by a shaft 24. A motor generally indicated by the reference character 25 is provided for operating the shaft 24, and this motor may be a proportioning `motor of the type illustrated in Patent 2,028,110 issued Jan. 14, 1936, to D. G. Taylor. This'motor may include a pair of armatures 21 .and 28 which are selectively energized by the eld windings 29 and 3|).l

Armatures 21 and 28 may be carried by a shaft 3| which is connected by means of suitable reduction gearing 32 to a gear 33 carried on the shaft 24. Upon energzation of the eld winding 29, the armature 21 rotates inva direction to cause the valve 28 to be moved towards closed position', and upon energization of the field winding 30 the armature 28 is rotated to cause valve 28 to be moved towards open position.

The energizaton of eld windings 29 and 38 is controlled by a relay generally designated by the reference character 35. clude a vpair of opposed balanced relay coils 36 and 31 vsuitably connected together -at one end thereof, and an armature 38 connected to a switch arm 39 which cooperates with xed contacts 40 and 4|. VWhen coils 36'and 31'are equally energized they exert an equal force on the' armature 38 and this armature remains in 'a mid position illustrated causing switch `arm 39 to remain midway between contacts v40 and 4|."

When relay coil 36 becomes more highly energized than lcoil 3-1 the armature 38 is attracted toward `the left and causes movement of arm 39 into' engagementwith the contact 46.1A When the relay coil 31 becomes'morefhighly energized than the coil 36 the armature 38 is attracted to the right and causes arm 39 to move-into engagement with the contact 4|. l

For supplying power -to the motor `,125 andv the relay 35 a step-down transformer-142 having a high tension primary 43 and a low tension secondary 44 may be provided. The primary 43.

side of secondary 44. 'On the otherv hand when the arm 3 9 is moved into engagement with the contact 4| by reason of relay coil 31 becoming more highly energized than coil 36, field winding 29 of the motor 25 isenergized through the following circuit: from the transformer secondary 44 through conductors 48, 49', arm-39,* contact 4|, conductor 53, eld winding 29, and conductors and 52 to the other side of secondary 44. It will now be apparent that when the relay coil 36 is more highly energized than coil 31, field winding 30 of motor 25 is energized and the valve is moved towards open position. Likewise when coil 31 becomes more highly energized than coil 36 eld winding 29 is energized causing the motor to move thevalve 20 towards closed position.

n The energization of the relay coils 36 and 31 Relay 35 may' inis controlled primarily by a differential pressure f controller represented generally by the reference character 55. This controller may include a pair of bellows 56 and 51 connected together by a rigid bar 58. Bellows- 56 is connected by means of a capillary tubey 59 to a bulb 66 mounted in' intimate contact with the inlet of the cooling coil |8. The bellows 51 isconnected byvmeans of a capillary tube 6| to a bulb 62 which is mounted in intimate contact with the' outlet ofthe cooling coil I8. Both of the bellows, tubes, and bulb may be provided with a suitable volatile fill sov that upon a temperature change at `either' the inlet -or outlet of the 'coil I8 the bellows 56 ,or the bellows 5'| will tend to expand or contract depending upon the change in temperature at the inletl or-outlet ofthe coil. The position of ro'd 58 will depend upon both the bellows 56 and 51 and since bellows 56 responds to the temperatureon, the inlet side of the coil I8 and bellows 51 responds-to the temperature at the outlet side of the coil theposition of the rod 58 willdepend upon. the differential: in tem-1v perature between the inlet and .outletaof-"the' coil I8. Thus if the temperaturey differential should decrease by reason of a drop in temperature at kthe outlet of the coil |8 or bynreason of a rise in temperature vat the inlet-of the'coil the rod 58`will be caused tomoveto the right. On the other hand if the temperature differential increases rod 58 will be moved toward thev left.

Carried by the rod end of the lever 18 is'biased by means ofak spring 12 atv the opposite end ofthe leverconnected to an adjusting Vscrew 13 into` engagementk with l.

the end 68 of the lever 61.'. Rigi'dly,connected4 to the lever18- is an arm 14 suitably insulated at 15 from the lever-10. Arm 1 4 is arranged to sweep across ya resistance 16,` this arm` 14 and resistance 16 forming a control potentiometer for the relayw'35.

|8, the lever 61 is` caused'7 to rotate in a clockwise direction which in turn causes the arm 14|l nected by means v.of conductors 96 and 80 and a center tapped resistance to the varm' 14. The opposite end ofV coil 31 is connected by ,means of conductors 52 and 8l and the protective resistance 82 to one side of-the secondary 44 of vtransformer 42. The other side of this secondary is connected by means ofA conductors 48 and 83 and the protective resistance 84 to the .other side of the relay coil 36. The left end of relay coil 36 is also connected by means of protective resistance 84 and the conductor 86 to the left end.

of resistance 16. 'The opposite end of this resistance is connected by means of conductor 81 land protective resistance 82,to the right end of l the relay coil 31.

With the arm 14 in the mid position as illustrated it will be-apparent that coils 36 and31 will be equally energized. Should the arm 14 be moved towards the right by reason of an increase in temperature differential through the 58 is` avpinr 65 received by the bifurcated end 66 ofthe bell crank lever,`

As the rod 58 4moves yto lthe left j byreason of an increase in the temper ure dif-. ferential between the inlet and outlet o the coil coil I8, the resistance in series with the relay coil 36 will be decreased whereas resistance in series with coil 31 will be increased. Coil 36 will therefore be more highly energized than coil 31 and armature 38 will be attracted toward-the left thus energizing the eld winding 30 causing resistance II3 is connected by means of conducan increase in temperature of the air entering opening movement of the valve 20. On the other hand should the arm 14 be moved towards the left by'reason of a. decrease in the temperature differential, the resistance in series with coil 31 will become less than that in series with the coil 36 and eld winding 29 of motor 25 will be energized thus causing closing movement of the valve 20. It will now be seen that upon an increase in temperature differential across the coilA I8, the valve is opened to increase the ow of the relay coils 36 and 31. The left end otresistance 9I is connected by means of conductors 91, 98, and protective resistance 84 to the left end of coil 36. The opposite end of resistance 9| is` `connected by means of resistance 99, conductor' |00, and protective resistance 82 to the right end of the coil 31. It will now be seen that this potentiometer is connected in parallel with the relay coils 36 and 31 and the potentiometer formed by resistance 16`and arm 14. The arm 90 is moved in an opposite sense to the arm 14 the return air inlet I2, the bellows |01 expands and causes arm ||2 to move toward the right which has the eiect of decreasing the resistance in series with the coil 36 and increasing the resistance in series with the coil 31 thus causing the motor to impart an opening movement to the valve 20. Since the resistance II6 is in the circuit to the rcontrol arm II2, this control arm will be less sensitive than the control arm 14 vof the control potentiometer. A movement of the arm II2 has the effect therefore of shifting the control range D of the arm 14, a. movement of I the arm II2 to the right in response to an inupon rotation of the motor 25 to counteract the effect of movement of arm 14. In other words, upon an increase in differential across the coil I8 the arm 14 moves to the right causing energization of eld winding 30 and the opening of valve 20. Upon rotation of the motor 25 the arm 90 is moved towards the left and when this arm has moved sufficiently far so as to cause a rebalancing of the relay coils 36 and 31 the armaure 38 will move back to mid position thus interrupting the operation of the motor 25. By reason of the provision of resistance element 93 in the circuit to arm 90, this arm must move over a relatively large distance to counteract the effect of aI smaller movement of the arm 14. In other words, a movement of arm 14 through the distance D may be suicient to cause movement of the valve 20 from closed to wide open positions and in order to rebalance the coils 36 and 31 the arm 90 will` have to move' through a much greater distance such as from one end of the resistance 9| tothe other. Y y

Mounted in the return air inlet I2 is a bulb |05 connected by means of a. capillary tube |06 to a bellows I 01, this tube, bulb, and bellows being lled with a suitable volatile fluid. Pivoted at |08 is a lever |09 having one end held by means of an adjustable spring IIO against a pin III-or other suitable vmember connected to the upperl portion ofthe bellows |01. Rigid with the lever |09 and suitably insulated therefrom is an arm II2 arranged to sweep over resistance II3, this arm and resistance forming a compensating potentiometer for the relay 35. The arm |I2 is connected to the junction of coils 36 and 31 by means of conductors II5, resistance II6, and

conductors ||1, 95, and 96. 'I'he right end of the crease in the return air temperature having the effect of shifting the control range D of arm 14 to the left so as to maintain a smaller differential in temperature across the coil I8. On the other hand if the return air temperature drops, causingarm ||2 to move toward the left over resistance I I3, relay coil 31 becomes more highly energized-than coil 36 and motor 25 operates to rclose the valve 20 and the control range of the arm 14 is moved towards the right to maintain a. higher temperature dierential across the coil I8. The provision of the center tapped resistance 85 insures that the controlrange D will have the same llength regardless of theposition of this control range over resistance 16.

It will now be seen that in the form of inven,

tion shown in Figure l, for any given temperature in the space I5, the valve 20 will operate to maintain a predetermined temperature differential f:

across the coil I8 so that the water being circulatedtherethr`ough is used most effectively. If however the temperature within the'space I5 increases, this increase being reflected by the bulb |05 and bellows |01, a greater need for cooling is indicated and valve 20 is then operated to maintain a lower temperature diiferential across the coil I8, the control range of the controller 14. being shifted towards the left.. On the other hand upon a drop'in temperature in the space I5 a smaller need for cooling is indicated and a higher diierential of temperature is maintained across the coil I 8, the control range of the arm 14 now being shifted towards the right over resistance 16. It should be understood that resistances 93 and I I6 may be variable resistances in order that the operating characteristics of the system may be controlled.

Referring now to the form of invention shown in Figure 2,-the water flowing through the coil I8 is assumed to have a uniform inlet temperature so that the valve20 need be controlled only in accordance with the temperature of the water leaving the coil I8 in order to obtain the same results as obtained in Figurey l. The motor 25 for operating the valve is not shown in detail in this gure but it will be understood that this motor may include two pairs of armatures and eld windings, the opposed balanced relay coils and the balancing potentiometer, all as described in connection with Figure l. The control potentiometer i is connected to the motor 25 inthe same manner as in Figure l and the arm 14 of this potentometer is operated by a single bellows |30, this bellows being connected by means of a capillary tube I3| to the bulb |32 mounted in vthe intimate contact with the outlet of the coil resistance between the terminals |33 and |34 of the motor whereupon the motor operates to move the valve towards open. position an amount proportional to the amount of movementv of the arm `14 ,over the resistance 16. If the temperature at |32 drops, indicating the water is being supplied to the coil I8 faster than is necessary for cooling purposes, arm 14 is moved toward the right, the resistance between theterminals |34 and |35 is decreased and the motorl causes the valve to be moved towards closed position. The action of the control arm 14 is compensated by the control arm ||2 which moves in response to variations in return air temperature in the same mannervas disclosed in connection with Figure 1.

It will now be apparent that the system of `Figure 2 is substantially the same as in Figure l above the desired value the valve 20 will be con. y Y trolled by the potentiometer arm 14.

Referring now to Figure 4, my invention is illustrated/in connection with a refrigeration system for controlling the supply of cooling wa- `except that the arm 14 moves in accordance with variations in `temperature at the outlet of the coil l0 instead of moving in accordance with variations in temperature differential across the coil as in Figure 1. This arrangement is entirely satisfactory where the temperature of the water.

Ientering the coil is substantially the same at all which expands and contracts in accordance withv variations in return air temperature operates a `mercury switch |40 instead of the potentiometer a mercury switch 2|1.

arm H2 as in. Figures l and 2. The control arm A14 of the control potentiometer is connected to I8 in the same manner as in Figures 1 and 2Q However, when the return air temperature drops `to a predetermined low value, the mercury switch |42 will be tilted in the opposite direction whereupon terminals 34 and |35 of the motor 25 will be directly connected together as follows: from terminal |34 through conductor |44, terminals |41, |48 of the switch |40 and conductors |43- and |46 to the terminal |35. When theseterminals are directly connected together the motor 25l will operate to entirely close thelvalvel 20V and prevent thesupply of water to the coil I8, the arm 114 of the control potentiometer having no eifect `whatever onthe motor 25.l

y An-arm 22| is biased-by mea'ns of an adjust ter to the condenser thereof. This system may include a compressor 200 driven by a motor 20|, the outlet ofthe compressor being connectedyby a pipe 202 to the condenser coil 203, the outlet of the condenser being connected to a receiver 204, there being a thermostatic expansion valve 205 for controlling the flow of refrigerant from the receiver 204 to the evaporator 206. Refrigerant flows from the evaporator 206 through a pipe 201 to the inlet of the compressor 200. The operation ofsuch a system will be apparent to those skilled in the art. Lines 209 and 2|0 which'may be connected to a suitable source of power (not shown) are provided `for supplying power to the motor 20|. For controlling the operation of the compressor a suction pressure controller 2|2 may be provided, this controller including a bellows 2|3 connected by means of aI pipe 2|4 to the inlet of' the compressor. A lever 2I5 is biased 'by means of a spring 2|6 into engagement with the 4top of the bellows 2|3, and this lever carries A high pressure controller 2|8 may also be provided for controlling the operation of the compressor. This controller may include a bellows 2|9 connected by means of a pipe 220 to the outlet lof the compressor.

v able spring 222 intov engagement with the bel- Jlows 2|9, this arm being pivoted at 223 and It will therefore be seen that with the system illustrated in Figure 3, which may be applied eitherr to the systems 0f Figure 1 or 2, that when therefis a call for cooling within the space the mercury switch |40 will be tilted to the position means of a pipe 243.

carrying a mercury switch 224 at one end thereof. The circuit through the motor 20| is as -followsz from the line 2|0 through conductor 230, mercury switch 224 of the high pressure controller 2|8, conductor 23|, mercury switch 2|1' of the suction pressure controller 2|2, conductor 232 through the motor 20| and conductor 233 to the line 209. It will now be apparent that the motor 20| will operate as long as the suction pressure is above a predetermined value and the discharge pressure is below a predetermined value. Should the suction pressure drop to a'low enough value the switch 2|1 will be tiltedin the opposite direction from that illustrated and interrupt the circuit to the motor 20|. .Should the discharge pressure reach a predetermined high value, the switch -224 will be tilted bythe bellows 2|9 in the opposite direction from that illustrated and break the circuit to the motor 20|.

For lcooling the condenser 203 water may, be supplied tothe tank 240 housing the lcoil 203 by means of a pipe 24| controlled by the valve 242. The water may leave the condenser by A motor 250 similar to the motor 25 of Figures 1 to 3 is connected by means of a pinion 25| to a'rack 252 connected to the valve stem-253 whereupon the position of the valve is controlled in accordance with l the operation of the motor 250. The motor 250 is controlled `by the differential pressure controller 260 which may be similar to that of Figure` 1 and may include'bellows 26| and 262 connected by means of capillary tubes 263 and f 264 to bulbs 265 and 266 mounted in intimate contact with the inlet pipe 24| and outlet pipe 243, respectively, the tubes, bulbs, and bellows being provided with a suitable volatile ll. The lever 261 is operated in accordance with variations in temperature diiferential at 24| and 243 to move the control arm 210 with respect to resistance 21| in the same manner as ln Figurel 1. Upon an increase in temperature differential the arm 210 is moved towards the right and upon a decrease in temperature differential the arm 210 is moved towards the left. The motor terminal 212 is connected by means of conductors 21.5 and 216 to the center tapped resistance 211 across which the arm 210 moves. The terminal 213 is connected by means of conductors 218 and 28| to the left end of resistance 21| and the terminal 214 is connected by means of conductors 280 and 219 to the right end' of resistance 21|. As the temperature differential at 24| and 243 increases the arm 210 is moved towards the right thus decreasing the resistance between the terminals 212 and 214 and causing the motor to move the valve towards open position an amount which is proportional to the increase in temperature differential.

The arm 22| carries a control arm 285 suitably insulated therefrom and forming the arm of a compensating potentiometer having a resistance 286., The arm 285 is connected by means of conductors 281, resistance 288, conductors 289 and 215 to the motor terminal 212. The right end of the resistance 286 is connected by means of conductors 290 and 218 to the motor terminal 213 and the opposite end of this resistance is connected by me'ans of conductors 29| 'anad 288 to the terminal 214 of the motor 250. As the pressure on the discharge side of the compressor 200 increases the bellows 2|9 will expand and cause the control arm 285 to move towards the leftover resistance 286 which will decrease the resistance connected between the terminals 214.and 215 whereupon the valve 242 will be moved towards open position. nected in the circuit to the arm 285 this arm will have less effect on the motor than the arm 210 and will have the effect ofshifting the control range of the arm 210 as the discharge pressure of the compressor 200 varies in the same manner that the control range of the control potentiometer arm 14 of Figure 1 is shifted in accordance with the return air temperature.

It will accordingly be seen that with the system shown in this gure for a given discharge pressure on the compressor the temperature differential between the inlet 24| and the outlet 243 for the condenser cooling water will be effectively controlled by controlling the amount of water supplied to the condenser whereby wasting of cooling water is eliminated. As the discharge` pressure on the compressor increases, a need for further cooling of the condenser is indicated and the control arm 285 is shifted towards the left thus shifting the control range of the arm 210 to the left to maintain a lower differential in temperature between the inlet pipe 24| and the outlet pipe 243 so that the increased cooling of the condenser which is required will be effected.

Referring now to Figure 5 a refrigeration system generally similar to that of Figure 4 is illustrated, this system including the compressor 200, condenser 203, receiver 204, expansion valve 205, and evaporator 20B. The circuit for controlling` scriptlon is unnecessary thereof. It should be understood however that the control circuit for the compressor motor of Figures 4 and 5 may be modied in anyI of the manners well known ln the art.

The control means for the valve 242 is shown to comprise a direct operating differential pressure controller 300 in place of the motor 250 controlled by the differential pressure controller 260 and the compensator 2|B of Figure 4. The valve stem 253 of the valve 242 is connected to a lever 30| pivoted at 302 and biased by means of an adjustable spring 303 in a counter-clockwise direction. A bellows 304 connected by means of a capillary tube 305 to a bulb 30G-mounted in intimate contact with the inlet pipe 24| which acts directly upon one side of the lever 30|. A

` sscond bellows 3I0 is connected by means of a capillary tube 3|| to the bulb 3|2 mounted in contact with the outlet pipe 243 and acts against the opposite side ofthe lever 30| in opposition with the bellows 3,04. It will be understood that both of these bellows, tubes, and bulbs will be filled with a suitable volatile uid and it will be seen that the position of -lever 30| will depend upon the relative pressures existing within the bellows 304 and 3|0 and therefore upon the temperature differential between the inlet pipe 24| and the outlet pipe 243. As the. temperature differential increases bellows 3I0 will exert an increasingly greater net force on the. lever 30|y and cause clockwise movement thereof and consequent opening of the valve 242 whereupon an increased supply of water is permitted by the valve 242 to decrease the temperature differential at 24| and 243. Also acting on the lever 30| in opposition to the bellows 304 is a bellows 3|5 connected by means of a pipe 3|6 to the discharge side of the compressor 200. As the discharge pressure increases the bellows 3|5 will expand and for a given temperature differential at the By reason of the resistance 288 con- E the operation of the compressor is shown as being identical to that of Figure 4 and further deinlet 24| and the outlet 243 an increase inthe discharge pressure on the compressor will have the eiect of moving the lever 30| in a clockwise direction thus further opening the valve` 2'42.

It will be apparent that with this system the valve 242 is operated in accordance wit "the differential in temperatures at the inlet 24| and the outlet 243,` this movement of the valve being compensated by the pressure on the discharge side of the compressor so'as to maintaina lower temperature differential' as the discharge pres-l1 sure increases and conversely to maintain a higher differential as the discharge pressure decreases. This system is direct acting and: eliminates the use of an electric motor as in Figures l to 4. It should be understood of course that the system illustrated in Figure-5 would also be applicable to a cooling system of the type shown in kFigures l to 3, the bellows 3|5 being connected to a bulb responsive to return air temperature or space temperature if applied to a system as shown in Figure 1.

Figure 6 shows another form of self contained unit wherein the operating mechanism maybe built rlgnt into the valve mechanism. The inlet pipe to the condenser is illustrated at 24| and controlled by the valve 242. The valve stem 253 is connected to the upper wall of a small bellows 320, this valve being biased towards closed.posi A cap 322 is casing and forms an enclosed chamber which maybe provided with a suitable volatileiill. The temperature of the water llowing past the valve 242 will be communicated to the volatile iill enclosed by cap'322 by the wall 330. Depending from the upper wall of the casing 322 is a small bellows 324 whose lower end is connected to the valve stem 253, the upper end of this bellows being sealed to the upper wall of the casing 322. A pipe 325 may connect this small bellows tothe high pressure side of the compressor. Also sealed to the top of the casing 322 is`a Ilarge bellows 326 which may be concentric ith the bellows 32'4 and also suitably connected t its lower end to the valve stem 253. A capillary tube 321 may connect this large bellows to a bulb mounted on the discharge side of the condenser, this large bellows, tube, and bulb being lled with a suitable volatile fluid. l

The bellows 326 will be expanded upon an increase in temperature at the discharge side of the condenser by reason of an increase in pressure of the volatile fill therein, and will be contracted` by reason of an increase in pressure of the volatile fill surrounding this bellows upon an increase in temperature at the inlet side of the condenser. This bellows will accordingly cause the valve 242 to assume positions depending upon the diierential in temperature at the inlet and the outlet side of` the condenser to increase the supply of water whenV the diierential increases to reduce the supply of water as the differential decreases. As the pressure on the high pressure side of the compressor increases, the force exerted by the bellows v324 vwill'increase and its eect is added to the eiect of the bellows 326 whereupon a lower diierential in temperature will cause an equal opening of the valve. In other words, to open the valve a given amount it will take a smaller differential in temperature if the discharge pressure of the compressor is higher than is required when the discharge pressure is low.

It will therefore be seen that by using a self contained valve unit of the type shown in Figure `6 the supply of water may be controlled in the same manner as in Figure without the use of an electric motor; It should be understood that this type of a valve operating mechanism could be applied to the systems illustrated in Figures 1 and 2 as well as to the systems of Figures 4 and 5. In such a .case the bellows 324 would respond to the return air temperature ywhereby thevalve position would be compensated iny accordance with the return air temperature as in Figures 1 and 2.

Having described the preferred forms of my invention many modifications and many adaptations may become apparent to those skilled in the art and it should be understood that my invention is limited only by the scope of the appended claims. Y

I claim as my invention:

1. In a system of the class described, temperature changing means, a valve for controlling the flow of a temperature changing medium through said temperature changing means, a motor for controlling the position of said valve, an expansible device responsive to the temperature of the temperature changing medium entering said temperature changing means, an expansible device responsive to the temperature of the temperature changing medium leaving said temperature changing means, circuit controlling means for said motor controlled by the conjoint action of said expansible devices for positioning the valve in response to changes in temperature differential between the inlet and outlet of said temperature'changing means, and means responsive to a condition which is a measure of a need for .more or less temperaturechanging for varylng the eiect of said circuit controlling means on the motor.

2. In a system of the class described, temperature changing means, a valve for controlling the i'low of a temperature changing medium through said temperature changing means, a motor for controlling the position of said valve, an expansible device responsive to the temperature of the temperature changing medium entering said temperature changing means, an expansible device responsive to the temperature of the temperature changing medium leaving said temperature changing means, circuit controlling means for said motor controlled by the conjoint action of said expansible devices for positioning the valve in response to changes in temperature differential 'between the inlet and outlet of said temperature changing means, and means respon- 'sive to the temperature of a space being controlled by said temperature changing means for varying the eiect of said circuit controlling means on the motor.

3. In a system of the class described, a cooling unit, a valve for controlling the iiow of a cooling medium through said unit, a motor for controlling the position of said valve, an expanslble device responsive to the temperature of the cooling medium entering said cooling unit, an expansible device responsive to the temperature of the cooling medium leaving said unit, circuit controlling means for said motor controlled by the conjoint action of said expansible devices for positioning the valve in response to changes in temperature differential between the inlet and outlet of ysaid unit, and means responsive to the attainment of a low predetermined temperature in a space being cooled by said unit for controlling said ow controlling means to prevent the ow of the cooling medium through said unit.

4. In a system of the class described, a cooling unit, a valve for controlling the flow of a cooling medium through said unit, a motor for controlling the position of said valve, an expansible device responsive to the temperature of the cooling medium entering said cooling unit, an expansible device responsive to the temperature of the cooling medium leaving said unit, circuit controlling means for said motor controlled by the conjoint action of said expansible devicesh for positioning the valve in response to changes in temperature dierenti l between the inlet and outlet of said unit, andgmeans responsive to the attainment of a predete mined low temperature in a space being cooled by said unit for causing said motor to rotate to a position in which said valve prevents the flow of cooling medium through said unit and rendering said circuit controlling means inopera ive.

5. In a system of the class described, temperature changing means, a valve for controlling the ilow of a temperature changing medium through said temperature changing means, an electric motor for controlling the operation of said valve, a device responsive to a conditiony which is a measure of the diierence in temperatures of the medium at the inlet and outlet of said temperature changing means, meansvr lincluding circuit controlling means operated by said device for controlling the operationA of said 'electric motor and valve', means responsive to a condition which is a measure of a need for morecr less temperature changing, and means including circuit conelectric motor and valve.-

means'for also controlling the 'operation of said 6. yIn an air conditioning system, a'n air conditioning chamber, a cooling coil through which a cooling medium circulates, the cooling medium entering said coil at a xed temperature, an

` electrically operated valve controlling the flow f to the values of said first and second variable resistance means for controlling the energization n of the valve operator.

7. In a system of the class described, temperature changing means, a valve for controlling the flow of a temperature changing medium through said temperature changing means, an electric motor for controlling the position of said valve, a device responsive to the temperature of the temperature changing medium entering said temperature changing means, a device responsive to the temperature of the temperature changing medium leaving said temperature changing means, motor controlling means including variable resistance means controlled by the conjoint effects of said devices to position the valve in response to changes in temperature diierential between the inlet and outlet of said temperature changing means, and means responsive to a condition Which is a measure of a need for more or less temperature changing for varying the action of said motor controlling means.

8. In a system of the class described, a cooling unit, a valve for controlling the ow of a cooling medium through said unit, a motor for controlling the position of said valve, a rst variable resistance means responsive to the temperature of the cooling medium entering said cooling unit, a second variable resistance means responsive to the temperature of the cooling medium leaving said unit, motor controlling means controlled by the conjoint eiects of said variable resistancemeans to, position the valve in response to changes in temperature diierential between the inlet and outlet of said unit, and means responsive to the attainment of a low predetermined temperature in a space being cooled by said unit for controlling said/valve to prevent the flow of the cooling medium through said unit.

9. In a system of the class described, a cooling unit, a valve for controlling the flow of a cooling medium through said unit, a motor for controlling the position of said valve, a device including electrical resistance means responsive to the temperature oi the cooling medium entering said cooling unit, a device including electrical resistance means responsive to the temperature of the cooling medium leaving said unit, motor controlling means including an electrical circuit controlled by the conjoint action of said devices to position the valve in response to changes in temperature differential between the inlet and outlet of said unit, and means in said circuit responsive to the attainment of a predetermined low temperature in a space being cooled by said unit for causing said motor to rotate to a position in which said valve prevents the ow of cooling medium through said unit and rendering said previously named motor controlling means ineffective.

WILLIAM L. MCGRATH. 

